<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			*{
				margin: 0;
				padding: 0;
			}
			
			div{
				width: 300px;
				height: 300px;
				border: 1px solid #000;
				box-sizing: border-box;
				margin: 200px auto;
				background: linear-gradient(red,green);
			}
		</style>
	</head>
	<body>
		
		<div></div>
	</body>
</html>